The invention concerns systems for conveying discrete entities.
More particularly, it concerns a device for conveying discrete entities that has a support driven in continuous rotation around an axis and which carries a transfer arm.
The proposed transfer arm is telescopic and has an inner radial part attached to the support and an outer radial part that can slide with respect to the inner radial part along an extension axis in a plane appreciably perpendicular to the axis of rotation of the support. The extension of the arm is controlled by a cam system as a function of the angular position of the arm around the axis of rotation of the support.
The arm has a gripper head that is suitable for supporting at least one entity and which is mounted on the outer radial part of the arm rotatably around an orientation axis that is appreciably parallel to the axis of rotation of the support. The orientation of the gripper head is controlled by a cam system.
Conveyor devices of this type are found in container blow-molding machines in which the container is obtained through blow molding by introducing into a blow-mold a preform previously produced by injection molding. For example, these machines are used for manufacturing polyethylene terephtalate (PET) bottles. The preform is in the shape of a tube that is closed at one end, while the other end already has the final shape of the neck of the container.
The preform is placed inside the mold after being brought to a suitable temperature in a temperature conditioning oven. When inflated, each container is removed from the mold and sent to the outlet of the machine.
Numerous container blow-molding machines are of the rotary type. These have a carrousel that turns continuously around its axis and carries around its periphery a series of identical molds.
Transfer arm conveyor devices, also known as star-shaped transfer devices, make it possible to insert the preforms in the molds as well as to remove the containers once they are formed, without having to stop the carrousel. Variable extension transfer arms make it possible to avoid interference between the molds and the objects being transported.
Transfer arms like these are also used to place in a blow mold a body intended to be at least partly overmolded by the material of the container. This is particularly the case with handles associated with PET containers.
Moreover, it is sometimes necessary for the transported object to have a very specific final orientation. For example, in a blow-molding machine this could involve a particular orientation of the preform that has undergone a special heating in order to produce a flat bottle, or of the precise positioning of the handle in the blow mold.
However, there is an application in which the orientation of the gripper head of the transfer arms is particularly important: that is, xe2x80x9cdual impressionxe2x80x9d machines in which each blow mold has two cavities in order to produce two containers simultaneously. The transfer arms must then simultaneously place two preforms in the blow mold, each of the preforms being received in one of the cavities. Once the two containers have been formed, they must be retrieved simultaneously by a transfer arm the gripper head of which has two pairs of grips.
To do this, transfer arms are known that have orientable gripper heads of the type described above. This type of transfer arm is found on the xe2x80x9cdual impressionxe2x80x9d machines produced until now by the applicant. In these conveyor devices, the extension of the arm and the orientation of the gripper head are obtained by two cam systems that are independent of each other. Thus, the outer radial part of the arm has a cam follower that cooperates with a cam path so that it alone controls the extension of the arm. The gripper head, which is articulated at the end of the outer radial part, also carries a cam follower that cooperates with another cam path so that it alone controls the orientation of the head with respect to the arm""s axis of extension.
This device, although it has been satisfactory, has certain limits to the amplitude of the movements that can be obtained. Moreover, it requires specific means to be provided in order to maintain the two cam followers in their respective cam paths.
A purpose of the invention is therefore to propose a new design of these transfer arms that will allow these limitations to be overcome.
To that end, the invention proposes a device of the type described above, characterized in that the extension of the arm and the orientation of the gripper head are controlled by a single rocker that is articulated on the outer radial part of the arm and which carries two cam followers each of which cooperates with an independent cam path.
According to other characteristics of the invention:
the rocker and the gripper head are combined;
the rocker and the gripper head are distinct from each other, the rocker controlling the orientation of the head by means of a transmission device;
the rocker and the gripper head are connected to each other by means of a link;
the rocker and the gripper head are articulated on the outer radial part of the arm around two different axes;
the connected cam paths that control the extension of the arm and the orientation of the head are each laid out along a closed loop around the axis of rotation of the support; elastic return means are provided to retract the outer radial part of the arm to a position of less extension in such a way that the two cam followers, which are arranged on the rocker on either side of a line parallel to the axis of extension passing through the axis of articulation of the rocker on the outer radial part of the arm, are pressed radially inward against the respective cam path;
the elastic return means are interposed between the inner and outer radial parts of the arm;
the device has at least two superimposed fixed plates each of which extends in a plane perpendicular to the axis of rotation of the support, the outer edge of each of the two plates forming one of the two cam paths that control the extension of the arm and the orientation of the head;
the inner radial part of the arm is mounted on the support so that it can pivot with respect to the latter around a pivot axis that is appreciably parallel to the axis of rotation of the support, and the pivoting of the arm with respect to the support is controlled as a function of the angular position of the support around its axis;
the pivoting of the arm with respect to the support is controlled by a cam system;
the gripper head can simultaneously support two entities; and
the support has several identical transfer arms with orientable head.
The invention also concerns a facility for blow molding containers made of thermoplastic material from preforms previously produced by injection molding, characterized in that it has at least one conveying device incorporating any of the preceding characteristics.